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Why Is Wood Rotting ?

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Old 06-18-2012, 07:28 PM   #41
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Re: Why Is Wood Rotting ?


I'm sensing some moderation.....

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Old 06-18-2012, 09:49 PM   #42
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Re: Why Is Wood Rotting ?

Not to be a smart a55, but is it possible that it only seems like old stuff never rots because the old stuff that did rot was torn out and replaced long ago?

I mean, old or new, if wood is poorly detailed it will rot, and in a hurry. The old stuff that is still around may have been well detailed to begin with, or in such a location or exposure that it will never rot, no matter how poorly it was detailed.

Just sayin...
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Old 07-13-2012, 01:00 PM   #43
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Re: Why Is Wood Rotting ?

This is how we sell more wood, sell more wood...
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Old 07-19-2012, 12:28 AM   #44
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Re: Why Is Wood Rotting ?

Nothing you can't fix with 1/4 inch paint
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Old 07-23-2012, 02:06 AM   #45
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Re: Why Is Wood Rotting ?

100+ year old growth cypress gutter, soaked from trapped moisture, paint removed, no rot:
(cypress is in the same family as juniper, eastern white cedar and western red cedar)


Pertinent exerpt from Causes and Control of Wood Decay, Degradation & Stain - LSU AgCenter

(my notes in parentheses)

The three primary sources of wood degradation are fungi (decay or rot), insects and weathering. The organisms that decay wood have four basic requirements: moisture (generally 25 to 100 percent of dry-wood weight), oxygen, temperature (generally between 50 degrees and 95 degrees Fahrenheit) and food (the wood itself). We can control wood degradation by altering one or more of these requirements. A sawmill will often keep its logs moist under a sprinkler system to saturate the logs with water and create an anaerobic environment in which there is insufficient oxygen for most wood decay organisms and insects. Wood can undergo slow bacterial degradation in fresh water or be attacked by marine borers in brackish or salt water, however.
It is impractical for consumers to keep lumber under a sprinkler system or buried in mud! Most wood decay can be prevented by simply keeping the wood dry. If lumber is dried to 6-8 percent moisture content for indoor uses or 15-18 percent for outdoor uses, it should not decay if the moisture content is maintained below 20 percent. A common cause of wood decay is when untreated wood is alternately exposed to wet and dry conditions, as in ground contact, or when it collects moisture and remains moist for an extended period. To prevent this situation, either keep your untreated lumber dry or use treated wood if you suspect it will get wet in service.

A few native species in Louisiana offer natural decay resistance. Old-growth bald cypress and SYP harvested at the turn of the century have not been degraded in most antebellum homes in the South. This is partly because of chemical and density differences between the old-growth timber and today’s young forests. Also, many of these houses were built off of the ground to keep the wood dry, and the boards had a slight space between them for air circulation. Other Louisiana species, such as sassafras, live oak(used for bones of U.S.S. Constitution, Old Ironsides), Eastern red cedar(aka juniper), catalpa and black locust(great alternative to PT if you can find it), offer better-than-average natural decay resistance. In the West, redwood and Western red cedar offer natural decay resistance, particularly with heartwood lumber.

Wood-destroying fungi are grouped into three categories: brown rot, white rot and soft rot. These different fungi will attack the three different, main chemical components of wood: cellulose, hemicellulose and lignin. When wood-degrading fungi metabolize wood, a decrease in strength occurs. The extent of the strength loss will vary depending on the type of fungi involved, wood species and lumber dimensions. Louisiana and most of the Deep South are classified as a severe-risk area for wood decay.

Not all fungi that attack wood cause degradation. In fact, many are classified as wood-staining or mildew (mold) fungi because they discolor or stain wood rather than cause decay. These fungi typically develop because of poor lumber-drying practices or excessively wet conditions. Stain fungi do not cause strength loss but result in a lower grade for some grading lumber and are considered unfavorable by consumers because of their appearance. Stain is not as important for structural-grade lumber. Structural integrity is more important than aesthetical appeal in certain situations, such as rural fencing or construction. Consumers should be aware if they notice stain fungi even though no strength loss may have occurred, because conditions that favor stain fungi are often ideal for wood-degrading organisms.

Two common terms used to describe wood features are heartwood and sapwood. Heartwood is wood in the inner section of a log and is entirely composed of dead cells. This region has a higher concentration of extractives (phenolic-based compounds that make heartwood more decay resistant than sapwood). Sapwood is wood near the bark and is often lighter in color than heartwood. Nutrient translocation occurs only in sapwood. Although most wood species can be treated with a preservative, certain species are considered difficult to treat because of their permeability and anatomical features. Douglas fir, a western species, has below-average permeability and is classified as difficult to treat(thus the west coast and Canada's fir PT is far inferior to the east coast's SYP PT). Species such as white oak have inclusions in the vessels called tyloses.(these give white oak its rot resistance; red oak lacks these, therefore rots easily) These inclusions also decrease permeability and make treating more difficult. In general, lumber that has a high percentage of heartwood or is improperly seasoned will be more difficult to pressure treat. Southern yellow pine (SYP) characteristics make it useful for many applications and easily treatable. Most pressure-treated lumber in the South is Southern yellow pine.

Full pdf here for download: http://home.comcast.net/~s37d/pub2703wooddecay7_24_08.pdf

Cypress Old Growth(left) vs Cypress New Growth(right)

A recent job involved replacing an exterior staircase platform, which provided a good example of what 25 years of exposure to the weather does to fir. This was all hidden behind another 2x12, which had no rot on its face to indicate rot beneath:

The other 4x4(not visible), had rotted into a 1x1; it fell over on its own after the attached railing was removed.

Last edited by motaro; 07-23-2012 at 02:51 AM.
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Old 05-27-2018, 12:07 PM   #46
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Re: Why Is Wood Rotting ?

Originally Posted by Murwall View Post
You just going to keep reviving threads with a thumbs up?
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Old 05-27-2018, 03:15 PM   #47
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Re: Why Is Wood Rotting ?

I know, it's been rather annoying, must be trying to get his post count up or something?

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Old 05-27-2018, 04:50 PM   #48
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Re: Why Is Wood Rotting ?

deleted...post is 6 years old!


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